Rocking-type seismic isolation base for protecting structure against earthquake

ABSTRACT

A rocking-type seismic isolation base for protecting structure against earthquake includes a body having a configuration similar to a generally recognized flying saucer. The base serves as a buffer when a structure is horizontally displaced relative to a supporting foundation of the structure, and largely reduces the vertical displacement of the structure. The rocking-type seismic isolation base also allows the displaced structure to automatically return to its original position. The base is provided at a bottom with a space for an anti-slipping lock to mount and freely move therein, so as to prevent the rocking-type base from horizontally slipping in a condition exceeded the designed seismic vibration. The rocking-type base may be cooperatively used with a saucer spring to further mitigate the vertical vibration.

FIELD OF THE INVENTION

The present invention relates to a seismic isolation device applicableto the fields of civil engineering, construction, and mechanicalengineering; and more particularly to a rocking-type seismic isolationbase having a configuration similar to a generally recognized flyingsaucer and provided with a bottom space for mounting an anti-slippinglock therein.

BACKGROUND OF THE INVENTION

The currently available seismic isolation products for protecting astructure against earthquake mainly include lead rubber isolationbearings, friction-type isolation bases, etc. While the presentinvention and these conventional seismic isolation products employsimilar principles for the same purpose of seismic isolation, thepresent invention is quite different from the conventional products interms of its shape and mounting technique. According to a major seismicisolation principle, a seismic isolation product generally utilizesvarious kinds of components to enable a structure to have a swing periodlonger than the vibration period of a seismic origin, so as to achievethe object of seismic isolation.

It is known in general mechanical and seismic fields that when arelatively swinging component has different radiuses of swinging, thecomponent may have an extended swinging period.

SUMMARY OF THE INVENTION

A primary object of the present invention is to provide a seismicisolation device to mitigate the influences of earthquake on astructure.

To achieve the above and other objects, the seismic isolation deviceaccording to the present invention is a rocking-type seismic isolationbase including a body having a configuration similar to a generallyrecognized flying saucer. In a preferred embodiment of the presentinvention, the rocking-type seismic isolation base has a concavespherical upper surface having a relatively small rolling radius and aconvex spherical lower surface having a relatively large rolling radius.The base so designed may have a swinging period larger than that of aseismic origin to achieve the effect of seismic isolation.

The rocking-type seismic isolation base serves as a buffer when astructure is horizontally displaced relative to a supporting foundationof the structure, and largely reduces the vertical displacement of thestructure. The rocking-type seismic isolation base also allows thedisplaced structure to automatically return to its original position.

The rocking-type seismic isolation base is provided at a bottom with aspace for an anti-slipping lock to mount and freely move therein, so asto prevent the rocking-type base from horizontally slipping in acondition exceeded the designed seismic vibration.

The rocking-type seismic isolation base may be cooperatively used with asaucer spring and/or a plunger piston to further mitigate the verticalvibration.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure and the technical means adopted by the present inventionto achieve the above and other objects can be best understood byreferring to the following detailed description of the preferredembodiments and the accompanying drawings, wherein

FIG. 1 is a side view of a rocking-type seismic isolation base having aconcave spherical upper surface according to a preferred embodiment ofthe present invention for protecting a structure against earthquake,wherein an anti-slipping lock is associated with the base;

FIG. 2 is a side view showing the rocking-type seismic isolation base ofFIG. 1 before and after rocking;

FIG. 3 is a side view showing the rocking-type seismic isolation base ofthe present invention associated with an anti-slipping lock and a saucerspring assembly;

FIG. 4 shows the rocking-type seismic isolation base of FIG. 3 beforeand after rocking;

FIGS. 5-1, 5-2, and 5-3 are top, front, and side views, respectively, ofthe rocking-type seismic isolation base according to the preferredembodiment of the present invention, wherein the base is provided with abottom space for the anti-slipping lock to mount therein;

FIGS. 6-1, 6-2, and 6-3 are bottom, front, and side views, respectively,of a saucer spring assembly for rotatably mounted in the concavespherical upper surface of the rocking-type seismic isolation base ofthe present invention;

FIGS. 7-1, 7-2, and 7-3 are top, front, and side views, respectively, ofan anti-slipping lock for associating with the rocking-type seismicisolation base of the present invention, wherein the anti-slipping lockhas a ball-shaped locking head;

FIG. 8 schematically shows a rocking-type seismic isolation base havinga convex spherical upper surface according to a second embodiment of thepresent invention; and

FIG. 9 schematically shows a rocking-type seismic isolation baseaccording to a third embodiment of the present invention, wherein thebase has a concave spherical upper surface associated with a plungerpiston and a saucer spring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to FIG. 1 that is a side view schematically showing arocking-type seismic isolation base 1 according to a preferredembodiment of the present invention for protecting a structure againstearthquake.

As shown, the rocking-type seismic isolation base 1 of the presentinvention has a configuration similar to a generally recognized flyingsaucer, and includes a concave spherical upper surface 5 allowing acorrespondingly shaped member to rotate and slide thereon, and a convexspherical lower surface 6 allowing the base 1 to rotate and roll or rockon a foundation surface 2. The concave spherical upper surface 5 has aradius smaller than that of the convex spherical lower surface 6. Theconcave spherical upper surface 5 is in tight and firm contact with acontact surface of the same radius pre-provided on the structure, whilethe convex spherical lower surface 6 is in point contact with thefoundation surface 2.

When rolling or rocking, the base 1 moves horizontally relative to thefoundation surface 2. Since the rocking-type base 1 rolls or rocks tomove, a friction between the convex spherical lower surface 6 and thefoundation surface 2 is relatively small to allow the base 1 to easilymove horizontally. On the other hand, a friction between a slidingarticle and a supporting surface is relatively large. Therefore, thecondition of horizontal sliding would not occur under generallyrelatively small seismic vibration.

With the concave spherical upper surface 5 having a relatively smallrolling radius and the convex spherical lower surface 6 having arelatively large rolling radius, the base 1 so designed may have aswinging period larger than that of a seismic origin to achieve theeffect of seismic isolation. Meanwhile, as shown in FIG. 2, when thebase 1 rolls and moves, a center of sphere 7 of the concave uppersurface 5 of the base 1 before rolling is shifted to a point indicatedby a reference number of “8”. A geometrically positional relationbetween the center of sphere 7 and the center of sphere 8 indicates thatthe rocking-type seismic isolation base 1 provides a relatively largehorizontal displacement, compared to the relatively small verticaldisplacement.

From a comparison between the shifted center of sphere 8 and theoriginal center of sphere 7 of the concave spherical upper surface 5 ofthe rocking-type seismic isolation base 1, it can be seen from FIG. 2that the shifted center of sphere 8 is always offset from aperpendicular line 9 passing a bearing point of the rolling base 1. Itis also found the offset distance increases with the increaseddisplacement of the rolling base 1, which indicates the rocking-typeseismic isolation base 1 has the property of automatically returning toan original position.

While it is ensured the rocking-type seismic isolation base 1 would notslide to displace within the designed seismic vibration condition, anypossible special condition exceeded the seismic vibration designcondition must still be taken into consideration. For this purpose, thebase 1 is provided at the convex spherical lower surface 6 with a bottomspace 4 for an anti-slipping lock 3 to mount thereto, so as to enhancethe safety in using the rocking-type seismic isolation base 1 of thepresent invention. From an observation of a geometrically positionalrelation between the bottom space 4 and the anti-slipping lock 3, it isfound the bottom space 4 preferably has a curved inner surface toprovide an optimal moving condition for the anti-slipping lock 3.

Generally, when a seismic isolation device is cooperatively used with adamping device, it is possible to provide the whole structure with anenhanced earthquake-resistant condition. Therefore, it is stronglyrecommended that a structure should be designed to allow direct mountingof a vertical earthquake vibration cushion spring thereto, so as tocooperate with an overall earthquake resisting solution.

Please refer to FIG. 3. In a most preferred embodiment of the presentinvention, the rocking-type seismic isolation base 1 is associated with,in addition to the anti-slipping lock 3, a saucer spring assembly 10that is in contact with a structure 11. In this manner, the base 1 ofthe present invention not only provides the basic seismic isolationfunction, but also the effect of mitigating the vertical earthquakevibration. From FIG. 4, it can be clearly seen when the base 1 with theanti-slipping lock 3 and the saucer spring assembly 10 rocks, thestructure 11 is displaced from an original position 12 to a displacedposition 13. Again, the rolling or rocking base 1 with the anti-slippinglock 3 and the saucer spring assembly 10 produces a horizontaldisplacement relatively larger than a vertical displacement.

FIGS. 5-1, 5-2, and 5-3 are top, front, and side views, respectively, ofthe rocking-type seismic isolation base 1 according to the preferredembodiment of the present invention. As shown, the base 1 includes theconcave spherical upper surface 5, the convex spherical lower surface 6,and the bottom space 4 for the anti-slipping lock 3 to mount and freelymove therein. Therefore, the base 1 is allowed to rock and swing on thefoundation surface 2 as shown in FIGS. 1 and 3.

FIGS. 6-1, 6-2, and 6-3 are bottom, front, and side views, respectively,of the saucer spring assembly 10. As shown, the saucer spring assembly10 includes a saucer spring 15 provided on a top of a bearing device 14.The bearing device 14 defines a spherical contact surface 16 that fitlyand rotatably contacts with the concave spherical upper surface 5 whenthe bearing device 14 is directly mounted on the top of the base 1 tolink the base 1 to the structure 11, so as to mitigate the verticalearthquake vibration applied to the structure 11.

FIGS. 7-1, 7-2, and 7-3 are top, front, and side views, respectively, ofthe anti-slipping lock 3. As shown, the anti-slipping lock 3 has aball-shaped locking head for smoothly contact with the curved innersurface of the bottom space 4.

FIG. 8 schematically shows a rocking-type seismic isolation baseaccording to a second embodiment of the present invention. In the secondembodiment, the base 1 has a ball-shaped top defining a convex sphericalupper surface 17 having a center of sphere 7, and a convex sphericallower surface 6. The convex spherical upper surface 17 is fitly androtatably engaged with a corresponding concave spherical surface 19formed on a structure 18.

FIG. 9 schematically shows a rocking-type seismic isolation baseaccording to a third embodiment of the present invention. In the thirdembodiment, the base 1 has a convex spherical lower surface 6, and aconcave spherical upper surface having a center of sphere 7. A plungerpiston 20 is located on the top of the base 1 with a ball-shaped lowerend fitly and rotatably engaged with the concave spherical upper surfaceof the base 1. And, a saucer spring 21 is located between an upper endof the plunger piston 20 and a structure 22, which is provided with acavity corresponding to the plunger piston 20 and the saucer spring 21.With these arrangements, the plunger piston 20 may have a relativelylarge vertical stroke within a predetermined planar area.

1. A rocking-type seismic isolation base for protecting a structureagainst earthquake, comprising a body having a configuration similar toa generally recognized flying saucer, and including a spherical uppersurface allowing a member having correspondingly shaped matching surfaceto rotate and slide thereon, and a convex spherical lower surfaceallowing the base to rotate, roll, or rock on a foundation surface;wherein said spherical upper surface has a small radius relative to saidspherical lower surface.
 2. The rocking-type seismic isolation base forprotecting a structure against earthquake as claimed in claim 1, whereinsaid body is provided at said convex spherical lower surface with abottom space having a curved inner surface for an anti-slipping lockdevice to mount and freely rotate and move in said bottom space.